Redefining fetal evoked fields with biomagnetic recordings over the whole maternal abdomen

The development of a technique for the recording of fetal brain activity has been highly limited by the inaccessibility of the developing human brain in utero. Based on the needs of resolution and a noninvasive nature, only biomagnetic measurements are suitable for the determination of the integrity of the fetal brain on a routine basis. We have built a new biomagnetic measurement device dedicated to this task. The main construction concerns were those of patient comfort, ease of performance of standard measurements, and appropriate spatial and temporal resolution. Our initial evaluation of the instrument has shown that it is capable of obtaining signals traditionally regarded as evoked fetal fields. Our results also show that this interpretation has to be made very carefully and that a large scale array is more appropriate for the extraction of fetal brain signals. In future it will be necessary to develop more controlled protocols by combining fetal behavioural tests and fetal auditory evoked field (fAEF) recordings, to generate convincing evidence that reported fAEF are generated in the fetal brain.